A cohort of 108 unreferred, randomly selected elementary school students, diagnosed in the first grade for presence or absence of attention deficit disorder (ADD) and its constituent symptoms of inattention and impulsivity, will be followed up in seventh and eighth grade. Psychopathological, neuropsychological, and electrophysiological measurements will be made at this time to determine: (a) the degree to which a first grade diagnosis of ADD is reliable or persistent until seventh and eighth grade; (b) what abnormalities persist -- in the above measurement domains -- from first grade symptoms of ADD; and (c) the differential role of first grade inattention and impulsivity in the prediction of seventh and eighth grade abnormalities. Parents of the above probands will be measured in the same domains, with the addition of regional cerebral blood flow measurements during mnestic and selective attention task performance. The parent data will be used: (a) for the definition of child-parent correlations in the symptoms and measured manifestations of ADD, leading to the formulation and test of genetic hypotheses; and (b) for cross-validation of neuropsychological, electrophysiological, and regional cerebral blood measurements within the parent sample.